1. Where are the lungs located?

2. What do the tubes in the lungs carry?

3. What part of the air do we use in the body?

4. Tell how the air gets into the lungs.

5. What pa.s.ses from the blood into the air sacs?

6. Why should we breathe through the nose?

7. Why should you keep the fingers away from the nose?

8. What are the vocal cords?

9. Give two reasons why no one should spit on the floor.

10. Tell how alcohol harms the lungs.

CHAPTER XV

FRESH AIR AND HEALTH

=How much Air we Breathe.=--At every breath we take in about one pint of air. We breathe eighteen times each minute. Nine quarts of air therefore pa.s.s in and out of the lungs every minute. Air once breathed is not fit to breathe again. It contains waste and carbon dioxide which weaken the body.

If you breathe three full breaths into a wide-mouthed jar or bottle, it will contain so much of the carbon dioxide that a lighted candle or splinter will at once go out when thrust into the jar. A cat shut in a tight box two feet square and one foot high will die in less than a half hour.

Many years ago when the British and Hindoo soldiers were fighting each other, the Hindoos made prisoners of 146 of the British and locked them in a room about one half as large as a common schoolroom. There were only two small windows. During the night 123 of these men died because of the bad air.

[Ill.u.s.tration: FIG. 64.--The direction of the flame of the candle shows how the fresh air enters and the bad air leaves a room.]

=How much Air should enter a Room.=--The air laden with waste coming out of the lungs quickly mixes with the other air of the room. In this way all of the air in the room soon becomes impure. Forty children will give out nearly two barrels of air in one minute. In another minute this air has made all of the other air in the room unclean. It can still be breathed, but it makes children feel drowsy and lazy and may cause headache. They then do poor work.

To keep the air pure in a room, fresh air must be let in from the outside. If there are many in the room, the openings must be large or fans on a wheel must be used to force the air in. In the New York schools a little over a cubic yard of fresh air is forced into the room for each child every minute.

=How to get Fresh Air into a Room.=--When air is warmed it becomes lighter and rises. In many public buildings, fresh air heated by a furnace is forced into the rooms through pipes entering several feet above the floor. By a fan or heated flue the impure air is sucked out of the room through openings near the floor.

[Ill.u.s.tration: FIG. 65.--How the windows of your bedroom should be open to get the most fresh air.]

Changing the air in a room is called _ventilation_. To get plenty of fresh air in a room there must be one or more places for it to enter and one or more places for it to pa.s.s out. Where there is no furnace or fan, windows on one side of the room may be opened at the bottom to let in the air and the same windows opened at the top to let the impure air escape. _Do not sit in a draft_, but use a board or curtain to throw the air upward as it enters the window. _A room should not be kept too warm._ Sitting in a very warm room weakens the body and prepares it to take cold. The temperature of a living room should be between 65 and 70 degrees.

=Fresh Air while you Sleep.=--Thousands of people have weakened their bodies and brought on disease by sleeping in bad air. Many persons keep their windows so tightly closed during the night that the air smells bad in the morning. I knew a family who always slept with windows closed except in the very warmest weather. Three of the children died of tuberculosis, and a fourth one took the disease but was saved by keeping his windows wide open.

Bad air in the sleeping room makes one feel drowsy in the morning instead of refreshed by sleep. _Your windows should always be open while you sleep._ In cold weather a window should be open a foot at both the bottom and the top, or if there are two windows in the room, both may be opened at the bottom. In moderate weather the openings should be twice as large. A cap may be worn to keep the head warm, and the bed should be out of the draft.

=Fresh Air gives Health.=--Four hundred people die of tuberculosis in our country every day. A few years ago it was thought that no one could get well of this disease. Now three fourths of those in the first stages of the disease get well. The chief part of the cure is fresh air. Medicine is seldom used because no medicine will cure tuberculosis. Good food and rest are great helps.

Many of those with tuberculosis stay out of doors all day and at night sleep in tents or with all of the windows wide open, even in the coldest weather. Snow may blow in and the water in the room may turn to solid ice, but fresh air, the good angel of health, will give the body new strength and make it well and strong again.

[Ill.u.s.tration: FIG. 66.--This man is curing himself of tuberculosis by sleeping at night, and sitting by day, on this porch.]

Many years ago when the Indians lived in tents and often slept outdoors none of them had this dirty air disease of tuberculosis.

Since they have formed the habit of living in houses nearly one half of some tribes have become sick with this catching disease.

=Making the Lungs Strong.=--It requires over three quarts of air to fill your lungs. When you breathe quietly, less than one pint of air pa.s.ses in and out of your lungs. This shows that a large part of the lungs is not used. The air sacs at the top and in the bottom part of the lungs are seldom filled completely. It is in these places that disease begins.

Several minutes should be spent two or three times each day in exercising the lungs. Fill them completely with air many times. _Learn to breathe deeply while you are walking in the fresh air._ Hold the head up and the shoulders back so that every part of the lungs can be filled. _Sit straight. Your life depends upon your lungs._ Give them a chance to do their work and teach them to do it well.

[Ill.u.s.tration: FIG. 67.--Unhealthful position which squeezes the lungs so that they cannot work freely.]

=Tobacco and Pure Air.=--There is poison in the smoke of tobacco. This is shown by its effect on insects. Owners of greenhouses often buy the stems and other waste parts of tobacco. They pile it in a pan and after closing the doors and windows of the greenhouse tightly, set fire to it.

The smoke rises and fills the whole house. In less than an hour it has killed many of the bugs and beetles which were destroying the plants.

A person not used to tobacco will sometimes be made sick by sitting only an hour in a room where persons are smoking. It is wrong for smokers to poison the air which others must breathe. For this reason a smoking room should be well ventilated.

CHAPTER XVI

THE BLOOD AND HOW IT FLOWS THROUGH THE BODY

[Ill.u.s.tration: FIG. 68.--The cells in the blood. The two white ones were drawn while crawling. Much enlarged.]

=The Blood keeps the Body Clean within and gives it Food.=--Every tiny particle of the body, whether in the legs, arms, or head, must have food to keep it alive and help it do its work. It must also have oxygen, and it must be washed clean of its waste matter. All this is done by the streams of blood, which bathe every cell to bring it food and oxygen and to wash away its waste.

=Parts of the Blood.=--Blood consists of a clear, watery part called _plasma_ and many little bodies named _cells_. The liquid found in a blister is the clear part of the blood. The cells which float in the watery part are so little and so close together that more than a million are in each drop of blood.

A few of the cells are white, but most of them are red, and it is their color that makes the blood look red. Your body contains about one gallon of blood. It is carried through the body in branching tubes called _blood vessels_ (Fig. 70).

[Ill.u.s.tration: FIG. 69.--Photograph of the heart from in front with the lungs pinned aside. One fourth natural size.]

=The Blood Vessels.=--There are four kinds of blood vessels. They are the _heart_, the _arteries_, the _capillaries_, and the _veins_. The heart lies in the chest between the lungs. It squeezes the blood into the arteries. These carry the blood to all parts of the body. It then runs into the capillaries, which are tiny tubes connecting the arteries with the veins. The veins return the blood to the heart.

The blood flows so fast that it goes from the heart down to the toes and back again in a half minute.

=The Heart or Pump of Life.=--When the heart stops we die, because the blood can no longer flow to carry food and oxygen to the hungry tissues. The heart is a sac with thick walls of muscle. It is shaped like a strawberry and is about as large as your fist. Its cavity is divided into four parts. The two upper ones are called _auricles_ and the lower ones are named _ventricles_. The blood enters the auricles and then pours through an opening into each ventricle, from which it pa.s.ses out into the arteries.

=The Arteries or Sending Tubes.=--The blood is sent out from the heart through the arteries leading to all parts of the body. The chief artery is the _aorta_. It is larger than your thumb and extends from the heart down through the body in front of the backbone. It has more than twenty branches. All of these branch again and again like the limbs of a tree until they are finer than hairs.

A large tube, the _lung artery_, takes blood directly from the heart to the lungs. Here it branches into more than a thousand divisions, so that the blood can take in oxygen and give off to the lungs its waste.

[Ill.u.s.tration: FIG. 70.--Arteries, the tubes carrying the blood from the heart through the body. Only the chief vessels are shown on one side.]